Apparatus and method for determination of stroke volume using the brachial artery

• US 7,740,590 B2
• Filed: 06/22/2009
• Issued: 06/22/2010
• Est. Priority Date: 06/16/2004
• Status: Active Grant

• Current Assignee: Cordeus, Inc.
• Original Assignee: Cordeus, Inc.
• Inventors: Bernstein, Donald P.
• Primary Examiner(s): Hindenburg; Max
• Assistant Examiner(s): TOWA, RENE T
• Application Number:
  US12/489,335
• Publication Number:
  US 20090259132A1
• Time in Patent Office: 365 Days
• Field of Search: 600500-501, 600/504, 600/506, 600/513, 600/536
• US Class Current: 600/506
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

Provided herein are methods and apparatus for stroke volume determination by bioimpedance from a patient'"'"'s upper arm, or brachium, or a patient'"'"'s thorax, utilizing pulsations of the arteries contained therein. The apparatus includes two or more spaced apart alternating current flow electrodes positioned on the patient'"'"'s arm or thorax and two or more spaced apart voltage sensing electrodes positioned on the patient'"'"'s arm or thorax and in-between alternating current flow electrodes. The system and method utilizes voltage sensed by the voltage sensing electrodes to calculate a cardiogenically induced impedance variation value of the patient, and to determine a stroke volume of the patient by multiplying the cardiogenically induced impedance variation value by a volume conductor V_C and by a left ventricular ejection time T_LVE.

Claims

1. An apparatus for determining stroke volume by bioimpedance from a patient, comprising:

two or more spaced apart alternating current flow electrodes positionable on a patient;

two or more spaced apart voltage sensing electrodes positionable on the patient and between the alternating current flow electrodes;

an alternating current source electrically connected to the alternating current flow electrodes;

a voltmeter electrically connected to the voltage sensing electrodes; and

a processing unit in communication with the voltage sensing electrodes, wherein the processing unit is configured to use a voltage sensed by the voltage sensing electrodes to calculate a cardiogenically induced impedance variation value of the patient, and to determine a stroke volume of the patient by multiplying the cardiogenically induced impedance variation value by a volume conductor V_C and by a left ventricular ejection time T_LVE;

wherein the processing unit determines the volume conductor V_C as;

$V_C=\left(C_1-C_1<br><br>\frac{Z_0}{Z_c}+\frac{Z_0^2}{Z_c^2}\right)·<br><br>\left(C_2·<br><br>W·<br><br>C_3\right),$

where;

C₁ is at least 1.0 and no greater than 8.0,

Z₀ is a transthoracic base impedance or a static D.C. component of a total transthoracic impedance,

Z_c is a critical level of base impedance that is at least 15Ω and

no greater than 25Ω

,

C₂ is at least 0.10 and no greater than 0.75,

W is a kilogram weight of the patient, and

C₃ is at least 35 and no greater than 100.

2. The apparatus of claim 1, wherein the cardiogenically induced impedance variation value is a first or a second time-derivative of a cardiogenically induced impedance variation of the patient.

3. The apparatus of claim 1, wherein the left ventricular ejection time T_LVE is obtained from a first time-derivative of the cardiogenically induced impedance variation (dZ/dt) waveform.

4. The apparatus of claim 3, wherein a trigger for initiating processing of the dZ/dt waveform is obtained from an R wave of an antecedent ECG waveform or a peak of an antecedent dZ/dt waveform.

5. The apparatus of claim 1, wherein the left ventricular ejection time T_LVE is obtained from a pulse oximetry waveform (Δ

SpO₂(t)) or a first time-derivative dSpO₂(t)/dt thereof.

6. The apparatus of claim 1, wherein the left ventricular ejection time T_LVE is obtained from an applanation tonometry (pressure) waveform (Δ

P(t)) or a first time-derivative dP(t)/dt thereof.

7. The apparatus of claim 1, wherein:

C₁ is substantially 4,

Z_c is substantially 20Ω

,

C₂ is substantially 0.25, and

C₃ is substantially 70.

8. The apparatus of claim 1, wherein:

for all values of Z₀ less than 20Ω

, the processing unit determines that

$\left(C_1-C_1<br><br>\frac{Z_0}{Z_c}+\frac{Z_0^2}{Z_c^2}\right)$

is greater than 1.0, and

for all values of Z₀ at least 20Ω

, the processing unit determines that

$\left(C_1-C_1<br><br>\frac{Z_0}{Z_c}+\frac{Z_0^2}{Z_c^2}\right)<br><br><br><br>\mathrm{is}<br><br><br><br>1.0.$

1.0.

9. The apparatus of claim 1, wherein C₂ multiplied by C₃ is at least 10 and no greater than 35.

10. The apparatus of claim 9, wherein C₂ multiplied by C₃ is substantially 17.5 mL/kg.

11. The apparatus of claim 1, wherein:

$C_3=\frac{C_4}{{\left({\mathrm{BMI}}_N\right)}^y}=\mathrm{mL}<br><br>\text{/}<br><br>\mathrm{kg},$

wherein;

C₄ is at least 35 and no greater than 100,

BMI_N is a normalized body mass index that is at least 0.5 and no greater than 5.0, and

y is at least 0.25 and no greater than 1.0.

12. The apparatus of claim 11, wherein:

C₄ is substantially 70 mL/kg,

BMI_N is substantially 1.0, and

y is substantially 0.5.

13. The apparatus of claim 12, wherein:

${\mathrm{BMI}}_N=\frac{W}{C_5·<br><br>H^2}$

wherein;

H is the patient'"'"'s height in meters, and

C₅ is the patient'"'"'s ideal body mass index (kg/m²) of at least 10 and no greater than 100.

14. The apparatus of claim 13, wherein C₅ is substantially 24 kg/m².

15. A method of determining stroke volume by bioimpedance from a patient, comprising:

positioning two or more spaced apart alternating current flow electrodes on a patient;

positioning two or more spaced apart voltage sensing electrodes on the patient and between the alternating current flow electrodes;

providing an alternating current flow (I(t)) through the electrically conductive electrodes creating a current field;

measuring a voltage (U(t)) between the voltage sensing electrodes within the current field;

calculating a cardiogenically induced impedance variation value of the patient using the measured voltage (U(t));

determining a volume conductor V_C as;

$V_C=\left(C_1-C_1<br><br>\frac{Z_0}{Z_c}+\frac{Z_0^2}{Z_c^2}\right)·<br><br>\left(C_2·<br><br>W·<br><br>C_3\right),$

where;

C₁ is at least 1.0 and no greater than 8.0,

Z₀ is a transthoracic base impedance or a static D.C. component of a total transthoracic impedance,

Z_c is a critical level of base impedance that is at least 15Ω and

no greater than 25Ω

,

C₂ is at least 0.10 and no greater than 0.75,

W is a kilogram weight of the patient, and

C₃ is at least 35 and no greater than 100; and

calculating a stroke volume of the patient by multiplying the cardiogenically induced impedance variation value by the volume conductor V_C and by a left ventricular ejection time T_LVE.

16. The method of claim 15, wherein the cardiogenically induced impedance variation value is a first or a second time-derivative of a cardiogenically induced impedance variation of the patient.

17. The method of claim 15, further comprising:

obtaining the left ventricular ejection time T_LVE from a first time-derivative of the cardiogenically induced impedance variation (dZ/dt) waveform.

18. The method of claim 17, wherein a trigger for initiating a processing of the dZ/dt waveform is obtained from an R wave of an antecedent ECG waveform or a peak of an antecedent dZ/dt waveform.

19. The method of claim 15, further comprising:

obtaining the left ventricular ejection time T_LVE from a pulse oximetry waveform (Δ

SpO₂(t)) or a first time-derivative dSpO₂(t)/dt thereof.

20. The method of claim 15, further comprising:

obtaining the left ventricular ejection time T_LVE from an applanation tonometry (pressure) waveform (Δ

P(t)) or a first time-derivative dP(t)/dt thereof.

21. The method of claim 15, wherein:

C₁ is substantially 4,

Z_c is substantially 20Ω

,

C₂ is substantially 0.25, and

C₃ is substantially 70.

22. The method of claim 15, further comprising:

for all values of Z₀ less than 20Ω

, determining that

$\left(C_1-C_1<br><br>\frac{Z_0}{Z_c}+\frac{Z_0^2}{Z_c^2}\right)$

is greater than 1.0, and

for all values of Z₀ at least 20Ω

, determining that

$\left(C_1-C_1<br><br>\frac{Z_0}{Z_c}+\frac{Z_0^2}{Z_c^2}\right)$

is 1.0.

23. The method of claim 15, further comprising:

determining C₂ multiplied by C₃ is at least 10 and no greater than 35.

24. The method of claim 23, wherein C₂ multiplied by C₃ is substantially 17.5 mL/kg.

25. The method of claim 15, further comprising:

determining that

$C_3=\frac{C_4}{{\left({\mathrm{BMI}}_N\right)}^y}=\mathrm{mL}<br><br>\text{/}<br><br>\mathrm{kg},$

wherein;

C₄ is at least 35 and no greater than 100,

BMI_N is a normalized body mass index that is at least 0.5 and no greater than 5.0, and

y is at least 0.25 and no greater than 1.0.

26. The method of claim 25, wherein:

C₄ is substantially 70 mL/kg,

BMI_N is substantially 1.0, and

y is substantially 0.5.

27. The method of claim 26, wherein:

${\mathrm{BMI}}_N=\frac{W}{C_5·<br><br>H^2}$

wherein;

H is the patient'"'"'s height in meters, and

C₅ is the patient'"'"'s ideal body mass index (kg/m²) of at least 10 and no greater than 100.

28. The method of claim 27, wherein C₅ is substantially 24 kg/m².